Abstinence from cigarette smoking is associated with negative affect symptoms, such as anxiety, irritability, depression and craving. These symptoms present a major obstacle in cessation, and they are intensified under acute stressful situations. Mechanisms responsible for the stress- induced exacerbation of withdrawal symptoms are not known. Without specific knowledge of the biobehavioral mechanisms responsible for the effects of stress in smoking, targeted efforts to stress-precipitated smoking will remain limited. The long-term goal of this research is to determine how psychobiological responses to behavioral stress influence smoking behavior. The specific goal of this project is to evaluate cortisol responses to behavioral stress and to assess the extent to which smoking abstinence alters these responses in dependent cigarette smokers. Smokers and non-smokers will participate in two counter-balanced laboratory sessions conducted on two separate days (rest session and stress session). Smokers will be randomly assigned to one of two conditions: abstinence from smoking for 24 hours prior to each lab session or ad libitum smoking. During the laboratory stress session, behavioral stress will be modeled by work on an extended, interpersonally demanding stress (public-speaking) with an emphasis on social evaluation. Salivatory cortisol and self-report measures of withdrawal symptoms will be obtained during the two laboratory sessions and during the 24-hour period prior to each session. During lab sessions, we will also monitor heart rate, systolic and diastolic blood pressure, and measure stroke volume using impedance cardiography. Calculated valuables will include cardiac output, systemic vascular resistance, and rate-pressure product. The project will include men and women, and will explore gender differences in responses to abstinence from nicotine and to behavioral stress. Ultimately this work should lead to a better understanding of the biobehavioral mechanisms responsible for the increased desire to smoke under stressful situations, and to development of more effective intervention techniques for smoking cessation and relapse prevention.